Removable contrapropeller



July 10, 1928.

O. OVERGAARD REMOVABLE CONTRA PROPELLER Filed Nov. 25, 1927 oLAv OVER AARD, or BROOKLYN, NEW YORK, AssisNoR TosTAR ooiv'rRA PRorELLEB LTD. A/S., OF OSLO, NORWAY, A CORIPORAT ION OF NORWAY.

REMOVABLE oONTRAPRorELLnR Application filed November 25, 1927. SeriaLNo. 235,511.

This invention relates to contra-propellers of that class where the contra-propeller blades are attached or madefintegral with the rudder post." here contra-propellers of this description are'used, the rudder post is made separable from the stern post and skeg so that it may be removed when the main propeller has to be drawn off the pro peller shaft. It sometimes is necessary or desirable to remove the propeller from the propeller shaft without putting the boat in drydock. This can he done by shiftingthe load of the boat forward until the boat is tipped enough so that the hub of the peller comes above the water level. It 1s much more difficult, however, to bring the lower end of the rudder post to thesurface. "My invention provides for the removal of the rudder post out of line with the propeller without the necessity of detachingthe same from thevessel at the lower end. To this end, the invention comprises a: contraa propeller hinged at the lower end-and bolted at the upper end on a pivot with a fore and aft axis to the'stern post. Such a con tra-propeller when unbolted at the upper end'can be lowered away sidewise of the ship on its hinged lower end until it no longer interferes with the removal of the main propeller. I 1

An embodiment of the invention is illustra-ted'in the accompanying drawings, in which i Figure 1 is a side elevation of the stern part of a ship fitted with a contra-propeller of the ahove'description.

Figure 2 is a rear end view of the same. The stern post is shown atl, the: rudder at 2, the skeg at 3, the main propeller at it and the contra-propeller at 5 equipped contra-propeller blades 6. These with blades, of which two are, shown as form-o ing the verticalpart of the contra-propeller f proand two extending laterally from the same, a-re'so contoured as to catch and turn into a direct rearward motion the rotating stream 1 that is discharged from the main propeller,

- At 7 is shown a hinge having a fore and d aft axis connecting the lower end. of the 'contra-p-ropeller to' the skeg and a-tS are shown bolts whereby the upper end of the contra-propeller issecured to the stern post.

Vi hen it is desired to remove the main propeller, the ship may have its sternoi'aised enough to'brin'g the hub of the nmnpw peller abovethe surface of the water by weighting the forward part of the vessel, then after removalof the bolts-;8 the contra-propeller can be lowered by the aid of a blockand fall or othermeans until it, by swmgmg sidewise on itshinge 7 occupies a position such as shown by dottedlines in Figure 2, in which position it will b'e'ent-irely 4 out oit'the way of the'rearward movement of the main propellerinthe' proeess-ofsliding it off its shaft] W hen the propeller has the top;

-Iclaim j 1 -o c 1; The combination with the main pro peller of a vessel, ofva contra-propeller in axial alignment therewith, the said contrasupportadapted to allow the contra-propelbeen replaced the contra-propeller can'be' I hauled up out of the water and rebolted at 1 propeller having at its lower end a pivotal 75 ler to he swung sidewise out of line with the main propeller for the purpose ofremovmg, o

the latter. i

I, j 2. The combinationwiththe inainfpro peller of a vessel, of a contra-propeller in axial alignment therewitlnth'e said contra propellerflbeing bolted to the vessel at, its upper end and supported at its lower end by a pivot, th eaxis ofwhich is fore and aft.

- O AV OVEBGAARD. 

